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I I. 29: XolAV / I6JK- 77/ If- 



SOLAR/1018-79/14 

(\\eph WI43 



Solar Energy System 
Performance Evaluation 



STEWART-TEELE-MITCHELL 
SINGLE- FAMILY RESIDENCE 

Malta, New York 
November 1978 Through March 1979 

Z Ta*Lf 




U.S. Department of Energy 

National Solar Heating and 
Cooling Demonstration Program 

National Solar Data Program 




NOTICE 

This report was prepared as an account of work sponsored by the United States 
Government. Neither the United States nor the United States Department of Energy, nor 
any of their employees, nor any of their contractors, subcontractors, or their employees, 
makes any warranty, express or implied, or assumes any legal liability or responsibility for 
the accuracy, completeness or usefulness of any information, apparatus, product or process 
disclosed, or represents that its use would not infringe privately owned rights. 



This report has been reproduced directly from the best available copy. 



Available from the National Technical Information Service, U. S. Department of 
Commerce, Springfield, Virginia 22161. 



Price: Paper Copy $5.25 
Microfiche $3.00 



SOLAR/1018-79/14 

Distribution Category UC-59 



SOLAR ENERGY SYSTEM PERFORMANCE EVALUATION 



STEWART-TEELE-MITCHELL 
MALTA, NEW YORK 



NOVEMBER 1978 THROUGH MARCH 1979 



JAMES E. HUGHES, PRINCIPAL AUTHOR 
JERRY T. SMOK, MANAGER OF RESIDENTIAL SOLAR ANALYSIS 
LARRY J. MURPHY, IBM PROGRAM MANAGER 



IBM CORPORATION 
18100 FREDERICK PIKE 
GAITHERSBURG, MARYLAND 20760 



PREPARED FOR 

THE DEPARTMENT OF ENERGY 

OFFICE OF ASSISTANT SECRETARY FOR 

CONSERVATION AND SOLAR APPLICATION 

UNDER CONTRACT EG-77-C-01-4049 

H. JACKSON HALE, PROGRAM MANAGER 



TABLE OF CONTENTS 

Page 

1. FOREWORD 1-1 

2. SUMMARY AND CONCLUSIONS 2-1 

2.1 Performance Summary 2-2 

2.2 Conclusions 2-2 

3. SYSTEM DESCRIPTION 3-1 

4. PERFORMANCE EVALUATION TECHNIQUES 4-1 

5. PERFORMANCE ASSESSMENT 5-1 

5.1 Weather Conditions 5-2 

5.2 System Thermal Performance 5-4 

5.3 Subsystem Performance 5-9 

5.3.1 Collector Array and Storage Subsystem 5-9 

5.3.1.1 Collector Array 5-9 

5.3.1.2 Storage 5-12 

5.3.2 Domestic Hot Water (DHW) Subsystem 5-16 

5.3.3 Space Heating Subsystem 5-16 

5.4 Operating Energy 5-19 

5.5 Energy Savings 5-19 

6. REFERENCES 6-1 

APPENDIX A DEFINITIONS OF PERFORMANCE FACTORS AND SOLAR TERMS A-l 

APPENDIX B SOLAR ENERGY SYSTEM PERFORMANCE EQUATIONS B-l 

APPENDIX C LONG-TERM AVERAGE WEATHER CONDITIONS C-l 

APPENDIX D MONTHLY SOLAR ENERGY DISTRIBUTION FLOWCHARTS D-l 

APPENDIX E MONTHLY SOLAR ENERGY DISTRIBUTIONS E-l 



n 



LIST OF ILLUSTRATIONS 

FIGURES TITLE PAGE 

3-1 Solar Energy System Schematic 3_2 

5-1 Solar Energy Distribution Flowchart Summary 5-6 

D-l Solar Energy Distribution Flowchart - D_2 

November 1978 

D-2 Solar Energy Distribution Flowchart - D-3 

December 1978 

D-3 Solar Energy Distribution Flowchart - D-4 

January 1979 

D-4 Solar Energy Distribution Flowchart - D " 5 

February 1979 

D-5 Solar Energy Distribution Flowchart - D "6 

March 1979 



m 



LIST OF TABLES 

TABLES TITLE PAGE 

5-1 Weather Conditions 5-3 

5-2 System Thermal Performance Summary 5-5 

5-3 Solar Energy Distribution Summary 5-7 

5-4 Solar Energy System Coefficient of Performance 5-8 

5-5 Collector Array Performance 5-10 

5-6 Storage Performance 5-13 

5-7 Solar Energy Losses - Storage and Transport 5-14 

5-8 Domestic Hot Water Subsystem Performance 5-17 

5-9 Space Heating Subsystem Performance 5-18 

5-10 Operating Energy 5-20 

5-11 Energy Savings 5-21 

E-l Solar Energy Distribution - E-2 

November 1978 

E-2 Solar Energy Distribution - E-3 

December 1978 

E-3 Solar Energy Distribution - E-4 

January 1979 

E-4 Solar Energy Distribution - E-5 

February 1979 

E-5 Solar Energy Distribution - E-6 

March 1979 



TV 



NATIONAL SOLAR DATA PROGRAM REPORTS 



Reports prepared for the National Solar Data Program are numbered under speci- 
fic format. For example, this report for the Stewart-Teele-Mitchell project 
site is designated as SOLAR/1018-79/14. The elements of this designation are 
explained in the following illustration. 



SOLAR/1018-79/14 



Prepared for the 

National Solar 

Data Program 



Demonstration Site 



Report Type 
Designation 



Year 



Demonstration Site Number: 

Each project site has its own discrete number - 1000 through 1999 for 
residential sites and 2000 through 2999 for commercial sites. 

Report Type Designation: 

This number identifies the type of report, e.g., 

Monthly Performance Reports are designated by the numbers 01 (for 
January) through 12 (for December). 

Solar Energy System Performance Evaluations are designated by the 
number 14. 



Solar Project Descriptions are designated by the number 50. 

Solar Project Cost Reports are designated by the number 60. 

These reports are disseminated through the U. S. Department of Energy Technical 
Information Center, P. 0. Box 62, Oak Ridge, Tennessee 37830. 



VI 



1 . FOREWORD 

The National Program for Solar Heating and Cooling is being conducted by the 
Department of Energy under the Solar Heating and Cooling Demonstration Act of 
1974. The overall goal of this activity is to accelerate the establishment 
of a viable solar energy industry and to stimulate its growth to achieve a 
substantial reduction in nonrenewable energy resource consumption through 
widespread applications of solar heating and cooling technology. 

Information gathered through the Demonstration Program is disseminated in a 
series of site-specific reports. These reports are issued as appropriate and 
may include such topics as: 

o Solar Project Description 

o Design/Construction Report 

o Project Costs 

o Maintenance and Reliability 

o Operational Experience 

o Monthly Performance 

o System Performance Evaluation 

The International Business Machines (IBM) Corporation is contributing to the 
overall goal of the Demonstration Act by monitoring, analyzing, and reporting 
the thermal performance of solar energy systems through analysis of measure- 
ments obtained by the National Solar Data Program. 

The Solar Energy System Performance Evaluation Report is a product of the 
National Solar Data Program. Reports are issued periodically to document the 
results of analysis of specific solar energy system operational performance. 
This report includes system description, operational characteristics and 
capabilities, and an evaluation of actual versus expected performance. The 
Monthly Performance Report, which is the basis for the Solar Energy System 
Performance Evaluation Report, is published on a regular basis. Each para- 
meter presented in these reports as characteristic of system performance 
represents over 8,000 discrete measurements obtained each month by the National 



1-1 



Solar Data Network (NSDN). Documents referenced in this report are listed in 
Section 6, "References." Numbers shown in brackets refer to reference numbers 
in Section 6. 

This Solar Energy System Performance Evaluation Report presents the results 
of a thermal performance analysis of the Stewart-Teele-Mitchell solar energy 
system. The analysis covers operation of the system from November 1978 through 
March 1979. The Stewart-Teele-Mitchell solar energy system provides DHW pre- 
heating and space heating to a single-family dwelling located in Malta, 
New York. Section 2 presents a summary of the overall system results. A 
system description is contained in Section 3. Analysis of the system thermal 
performance was accomplished using a system energy balance technique described 
in Section 4. Section 5 presents a detailed assessment of the individual 
subsystems applicable to the site. 

The measurement data for the reporting period were collected by the NSDN [1]. 
System performance data are provided through the NSDN via an IBM-developed 
Central Data Processing System (CDPS) [2]. The CDPS supports the collection 
and analysis of solar data acquired from instrumented systems located through- 
out the country. This data is processed daily and summarized into monthly 
performance reports. These monthly reports form a common basis for system 
evaluation and are the source of the performance data used in this report. 



1-2 



2. SUMMARY AND CONCLUSIONS 

This section provides a summary of the performance of the solar energy system 
installed at Stewart-Teele-Mitchell , located in Malta, New York for the 
period November 1978 through March 1979. This solar energy system is designed 
to support the DHW preheating and space heating loads. A detailed descrip- 
tion of the Stewart-Teele-Mitchell solar energy system operation is presented 
in Section 3. 

2.1 Performance Summary 

The solar energy site was unoccupied from November through December 1978. The 
house was sold in late December and occupied in January 1979. With the excep- 
tion of the DHW subsystem, the solar energy system operated continuously 
during this reporting period. The DHW subsystem was activated in early 
January 1979. 

The total incident solar energy was 60.35 million Btu during the reporting 
period, of which 11.98 million Btu were collected by the solar energy system. 
Solar energy applied to the DHW and space heating loads was 5.38 million Btu. 
Solar systems losses were 6.51 million Btu. The cost of operating the solar 
energy system was 0.99 million Btu. 

Solar energy satisfied 13 percent of the DHW requirements and 9 percent of 
the space heating requirements for an overall solar fraction of 11 percent. 
The solar energy system provided a fossil fuel savings of 7.25 million Btu 
and incurred an electrical energy expense of 0.71 million Btu. 

The following incidents or conditions affected the solar energy system perfor- 
mance during the reporting period: 

The DHW loop pump (EP300) was not activated prior to January 1979. This contri 
buted to a low overall DHW solar fraction. 

Mode-determining valve V2 (D400) did not seat properly.. When the system was 
collecting energy, the heat transfer fluid divided at valve V2 and flowed to 

2-1 



both the solar coil in the space heating air loop and to the storage tank. 
The faulty valve was replaced in March 1979. 

The collector loop heat- transfer fluid (glycol/water) was frozen from February 9 
through February 15. 

2.2 Conclusions 

The actual performance of the solar energy system was considerably below the 
expected performance as measured by the expected solar fraction. The overall 
solar fraction of 12 percent is approximately one third of the expected 
value. A colder-than-expected winter was a contributing factor. However, 
this was partially offset by an average daily total insolation in excess of 
the long-term value. 

Two conditions can be identified that adversely impacted the DHW solar fraction. 
The first condition was of a temporary nature: no solar energy was applied 
to DHW preheating during 40 percent of the reporting period because pump P4 
(EP300) was turned off. The second condition is a matter of system design: 
the separate DHW preheat tank is incompatible with the small amount of water 
being used. Even when the preheat tank water temperature exceeds the thermo- 
statically-controlled auxiliary DHW tank water temperature, electrical energy 
is used to maintain the temperature of the water in the coventional DHW tank 
at the thermostat setting. The electrically-heated water in the conventional 
DHW tank often serves to temper the solar-heated water as it is drawn from 
the preheat tank. 



2-2 



3. SYSTEM DESCRIPTION 

The Stewart-Teele-Mitchell site is a single-family residence in Malta, New York 
The home has approximately 1900 square feet of conditioned space. Solar 
energy is used for space heating the home and preheating domestic hot water 
(DHW). The solar energy system has an array of flat-plate collectors with a 
gross area of 432 square feet. The array faces south at an angle of 45 
degrees to the horizontal. A glycol/water solution is the transfer medium 
that delivers solar energy from the collector array to a heat exchanger. 
Water is then used as the transfer medium that delivers solar energy from 
the heat exchanger to storage, and to the space heating and DHW loads. Solar 
energy is stored in the basement in a 1000-gallon insulated tank. Preheated 
city water is stored in a 75-gallon preheat tank a^d supplied, on demand, to 
a conventional 40-gallon DHW tank. When solar energy is insufficient to 
satisfy the space heating load, an oil-fired furnace provides auxiliary 
energy for space heating. Similarly, an electrical heating element in the 
DHW tank provides auxiliary energy for water heating. The system, shown 
schematically in Figure 3-1, has five modes of solar operation. 

Mode 1 - Collector-to-Storage : This mode activates when the collector tempera- 
ture exceeds the storage temperature by 20°F and terminates when a temperature 
difference of 3°F is reached. Solar energy is transferred through the heat 
exchanger that transmits energy from the solar collection loop to the storage 
loop. Collector loop pump PI and storage loop pump P2 are operating. 

Mode 2 - Col lector- to-Space Heating : This mode activates when mode 1 condi- 
tions are satisfied and there is a demand for space heating. The collected 
solar energy bypasses storage and flows directly to the solar heating coil in 
the air-handling system. Mode diversion valve V2 is open. 

Mode 3 - Storage- to-Space Heating : This mode activates when there is a 
demand for space heating, the temperature at the top of the storage tank 
exceeds 100°F, and solar energy from the collector is not available. Pump P3 
is operating. 



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Mode 4 - Storage-to-DHW Tank : This mode activates when the temperature at 
the top of the storage tank exceeds the preheat tank water temperature by 
10°F. Pump P4 is operating. 

Mode 5 - Summer Mode, Collector-to-Vent : This mode activates when the col- 
lector array output fluid temperature exceeds 220°F. The collected solar 
energy is rejected through a fintube heat exchanger located outside the 
dwelling. Valve VI directs the collector loop flow through a purge unit. 



3-3 



4. PERFORMANCE EVALUATION TECHNIQUES 

The performance of the Stewart-Teele-Mitchell solar energy system is evaluated 
by calculating a set of primary performance factors which are based on those 
proposed in the intergovernmental agency report "Thermal Data Requirements 
and Performance Evaluation Procedures for the National Solar Heating and 
Cooling Demonstration Program" [3]. These performance factors quantify the 
thermal performance of the system by measuring the amount of energies that 
are being transferred between the components of the system. The performance 
of the system can then be evaluated based on the efficiency of the system in 
transferring these energies. All performance factors and their definitions 
are listed in Appendix A. 

Data from monitoring instrumentation located ai key points within the solar 
energy system are collected by the National Solar Data Network. This data is 
first formed into factors showing the hourly performance of each system com- 
ponent, either by summation or averaging techniques, as appropriate. The 
hourly factors then serve as a basis for calculating the daily and monthly 
performance of each component subsystem. The performance factor equations 
for this site are listed in Appendix B. 

Each month, as appropriate, a summary of overall performance of the Stewart- 
Teele-Mitchell site and a detailed subsystem analysis are published. These 
monthly reports for the period covered by this Solar Energy System Performance 
Evaluation November 1978 through March 1979 are available from the Technical 
Information Center, Oak Ridge, Tennessee 37830. 

In the tables and figures in this report, an asterisk indicates that the 
value is not available for that month; N.A. indicates that the value is not 
applicable for this site. 



4-1 



5. PERFORMANCE ASSESSMENT 

The performance of the Stewart-Teele-Mitchell solar energy system has been 
evaluated for the November 1978 through March 1979 time period. Two per- 
spectives were taken in this assessment. The first views the overall system 
in which the total solar energy collected, the system load, the measured 
values for solar energy used, and system solar fraction are presented. Where 
applicable, the expected values for solar energy used and system solar fraction 
are also shown. The expected values have been derived from a modified f-chart 
analysis which uses measured weather and subsystem loads as input. The 
f-chart is a performance estimation technique used for designing solar 
heating systems. It was developed by the Solar Energy Laboratory, University 
of Wisconsin - Madison. The system mode used in the analysis is based on 
manufacturer's data and other known system parameters. In addition, the 
solar energy system coefficient of performance (COP) at both the system and 
subsystem level has been presented. 

The second view presents a more in-depth look at the performance of indivi- 
dual subsystems. Details relating to the performance of the collector array 
and storage subsystems are presented first, followed by details pertaining to 
the space heating and domestic hot water (DHW) subsystems. Included in this 
section are all parameters pertinent to the operation of each individual 
subsystem. 

In addition to the overall system and subsystem analysis, this report also 
describes the equivalent energy savings contributed by the solar energy 
system. The overall system and individual subsystem energy savings are 
presented in Section 5.5. 

The performance assessment of any solar energy system is highly dependent on 
the prevailing weather conditions at the site during the period of performance. 
The original design of the system is generally based on the long-term aver- 
ages for available insolation and temperature. Deviations from these long- 
term averages can significantly affect the performance of the system. Therefore, 



5-1 



before beginning the discussion of actual system performance, a presentation 
of the measured and long-term averages for critical weather parameters has 
been provided. 

5.1 Weather Conditions 

Monthly values of the total solar energy incident in the plane of the col- 
lector array and the average outdoor temperature measured at the Stewart- 
Teele-Mitchell site during the reporting period are presented in Table 5-1. 
Also presented in Table 5-1 are the corresponding long-term average monthly 
values of the measured weather parameters. These data are taken from 
Reference Monthly Environmental Data for Systems in the National Solar Data 
Network [4]. A complete yearly listing of these values for the site is given 
in Appendix C. 

From November 1978 through March 1979 the average daily total incident solar 
energy on the collector array was 936 Btu per square foot per day. This was 
above the estimated average daily solar radiation for this geographical area 
during the reporting period of 890 Btu per square foot per day for a south- 
facing plane with a tilt of 45 degrees to the horizontal. The average ambient 
temperature from November 1978 through March 1979 was 27°F as compared with 
the long-term average for November through March of 29°F. The number of 
heating degree-days for the same period (based on a 65°F reference) 5527, 
as compared with the long-term average of 5465. 

Monthly values of heating and cooling degree-days are derived from daily 
values of ambient temperature." They are useful indications of the system 
heating and cooling loads. Heating degree-days and cooling degree-days are 
computed as the difference between daily average temperature and 65°F. For 
example, if a day's average temperature was 60°F, then five heating degree- 
days are accumulated. Similarly, if a day's average temperature was 80°F, 
then 15 cooling degree-days are accumulated. The total number of heating and 
cooling degree-days is summed monthly. 



5-2 



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5.2 System Thermal Performance 

The thermal performance of a solar energy system is a function of the total 
solar energy collected and applied to the system load. The total system load 
is the sum of the useful energy delivered to the loads (excluding losses in 
the system), both solar and auxiliary thermal energies. The portion of the 
total load provided by solar energy is defined as the solar fraction of the 
load. 

The thermal performance of the Stewart-Teele-Mitchell solar energy system is 
presented in Table 5-2. This performance assessment is based on the five- 
month period from November 1978 to March 1979. During the reporting period, 
a total of 11.98 million Btu of solar energy was collected and the total 
system load was 51.40 million Btu. The measured amount of solar energy 
delivered to the load subsystem(s) was 5.38 million Btu or 11.57 million Btu 
less than the expected value. The measured system solar fraction was 11 per- 
cent as compared to an expected value of 33 percent. 

Figure 5-1 illustrates the flow of solar energy from the point of collection 
to the various points of consumption and loss for the reporting period. The 
numerical values account for the quantity of energy corresponding with the 
transport, operation, and function of each major element in the Stewart- 
Teele-Mitchell solar energy system for the total reporting period. 

Solar energy distribution flowcharts for each month of the reporting period 
are presented in Appendix D. 

Table 5-3 summarizes solar energy distribution and provides a percentage 
breakdown. For the period November 1978 through March 1979, the load subsys- 
tems consumed 45 percent of the energy collected and 54 percent was lost. 
Solar energy storage gain was 1 opercent over the period. Appendix E contains 
the monthly solar energy percentage distributions. 

The solar energy coefficient of performance (COP) is indicated in Table 5-4. 
The COP simply provides a numerical value for the relationship of solar 



5-4 



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5-5 



FIGURE 5-1. SOLAR ENERGY (MILLION BTU) DISTRIBUTION FLOWCHART - SUMMARY 

STEWART-TEELE-MITCHELL 



Incident 
Solar Energy 






■ 

Solar Energy 
Storage Losses 


60.35 








3.99 




1 






(1) 






Change in 
Stored Energy 




i 


Operational 
incident 
Solar Energy 




Transport Loss 
Collector to 
Storage 


ECSS Subsystem 
Operating Energy 












0.10 










40.70 


1.10 


0.48 




♦ 






1 
















i 
I 






Collected 
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Solar Energy 
to Storage 


i 


Solar Energy 
from Storage 










11.98 






(1) 


10.30 






Ml 


6.23 








Transport Loss 
Collector to DHW 








Transport Loss 
Storage to DHW 


















N.A. 























Domestic Hot 
Water Solar 
Energy Used 


























N.A. 


1.02 






DHW Subsystem 
Operating Energy 




Domestic Hot 
Water Auxiliary 
Thermal Used 






0.21 


2.51 










Domestic Hot 
Water Load 










(1) 




2.30 






d) 








Transport Loss 
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Space Heating 








Transport Loss 
Storage to 
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• 








1.43 














Space Heating 
Solar Energy Used 


























0.58 


3.78 






Space Heating 
Subsystem 
Operating Energy 




Space Heating 
Auxiliary Thermal 
Used 






3.12 


44.74 










Space Heating 
Load 










(1) 




49.10 














Transport Loss 
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Space Cooling 








Transport Loss 
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Space Cooling 


















N.A. 








N.A. 














Space Cooling 
Solar Energy Use^. 


























N.A. 


N.A. 






Space Cooling 
Subsystem 
Operating Energy 




Space Cooling 
Auxiliary Thermal 

Used 










(1) 


N.A. 


N.A. 














Total Loss - 
Collector to 
Storage and Loads 






Space Cooling 
Load 




Total Loss - 
Storage to Loads 








* 










* 


N.A. 


1.43 





(11 



* Denotes Unavailable Data 

N.A. denotes not applicable data 

(1) May contribute to offset of space heating Ipad (if known - see text for discussion) 

5-6 



S002 



TABLE 5-3. SOLAR ENERGY DISTRIBUTION - SUMMARY NOVEMBER 1978 THROUGH MARCH 1979 

STEWART-TEELE-MITCHELL 

11.98 million Btu T0TAL $()LAR ENERGY C0LLECTED 



100% 

5.38 mi' ion Btu 



45 % 



SOLA' 1 ENERGY TO LOADS 



ill ion ' tu $0LAR ENERGY T0 DHW SUBSYSTEM 



9 % 
4.36 million 1 tu 



36 % 
N.A. million t tu 



% 
6.52 million Btu 



54 % 

3.99 mi" 
33 % 

2.53 million Btu 



SOLAR ENERGY TO SPACE HEATING SUBSYSTEM 

SOLAR ENERGY TO SPACE COOLING SUBSYSTEM 
ENERGY LOSSES 

SOLAR ENERGY LOSS FROM STORAGE 

SOLAR ENERGY LOSS IN TRANSPORT 



21 % 

1 .10 million Btu 



jj COLLECTOR TO STORAGE LOSS 

* million Btu, 



COLLECTOR TO LOAD LOSS 
N.A. million Btu 



% 

million Btu 



% 
N.A. million Btu 



% 
1.43 million Btu 



COLLECTOR TO DHW LOSS 
COLLECTOR TO SPACE HEATING LOSS 
COLLECTOR TO SPACE COOLING LOSS 



j2~% STORAGE TO LOAD LOSS 

* mill ion Btu, 



lo 

1 .43 million Btu 



STORAGE TO DHW LOSS 



■j^Y STORAGE TO SPACE HEATING LOSS 

N.A. million Btu, 



% 
.10 million Btu 



'STORAGE TO SPACE COOLING LOSS 



TT 



SOLAR ENERGY STORAGE CHANGE 



* - Denotes unavailable data 5.7 
N.A. - Denotes not applicable data 



SPACE COOLING 
SUBSYSTEM 
SOLAR COP 


<: <s. <c < «c 

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z 


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lo co in s ro 

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energy collected or transported or used and the energy required to perform 
the transition. The greater the COP value, the more efficient the subsystem. 
The solar energy system at Stewart-Teele-Mitchell functioned at a weighted 
average COP value of 5.43 for the reporting period November 1978 through 
March 1979. 

5.3 Subsystem Performance 

The Stewart-Teele-Mitchell solar energy installation may be divided into 
three subsystems: 

1. Collector Array and Storage 

2. Domestic Hot Water (DHW) 

3. Space Heating 

Each subsystem is evaluated and analyzed by the techniques defined in Section 
4 to produce the monthly performance reports. This section presents the 
results of integrating the monthly data available on the three subsystems for 
the period November 1978 through March 1979. 

5.3.1 Collector Array and Storage Subsystem 

5.3.1.1 Collector Array 

Collector array performance for the Stewart-Teele-Mitchell site is presented 
in Table 5-5. The total incident solar radiation on the collector array for 
the period November 1978 through March 1979 was 60.35 million Btu. During 
the period the collector loop was operating the total insolation amounted to 
40.70 million Btu. The total collected solar energy for the period was 11.98 
million Btu, resulting in a collector array efficiency of 29 percent, based 
on total incident insolation. Solar energy delivered from the collector 
array to storage was 10.30 million Btu, while solar energy delivered from the 
collector array directly to the loads amounted to 0.58 million Btu. Energy 
loss during transfer from the collector array to storage was 1.10 million 



5-9 



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Btu. This loss represented 9 percent of the energy collected. Operating 
energy required by the collector loop was 0.48 million Btu. 

Collector array efficiency has been computed from two bases. The first 
assumes that the efficiency is based upon all available solar energy. This 
approach makes the operation of the control system part of array efficiency. 
For example, energy may be available at the collector, but the collector 
fluid temperature is below the control minimum; therefore, the energy is not 
collected. In this approach, collector array performance is described by 
comparing the collected solar energy to the incident solar energy. The ratio 
of these two energies represents the collector array efficiency which may be 
expressed as 

\ - V»i 

where: n = collector array efficiency 

Q = collected solar energy 

Q. = incident solar energy 

The monthly efficiency computed by this method is listed in the column entitled 
"Collector Array Efficiency" in Table 5-5. 

The second approach assumes the efficiency is based upon the incident solar 
energy during the periods of collection only. 

Evaluating collector efficiency using operational incident energy and com- 
pensating for the difference between gross collector array area and the gross 
collector area yield operational collector efficiency. Operational collector 
efficiency, n , is computed as follows: 

n co - Q /(Q x J&) 
a 



5-11 



where: Q = collected solar energy 

Q . = operational incident energy 

A = gross collector area (product of the number 
of collectors and the total envelope area of 
one unit) 

A = gross collector array area (total area perpen- 
a 

dicular to the solar flux vector, including all 
mounting, connecting and transport hardware 

A 
Note: The ratio -J^- is typically 1.0 for most collector array configurations. 

a 

The monthly efficiency computed by this method is listed in the column entitlec 
"Operational Collector Array Efficiency" in Table 5-5. This latter efficiency 
term is not the same as collector efficiency as represented by the ASHRAE 
Standard 93-77 [5]. Both operational collector efficiency and the ASHRAE 
collector efficiency are defined as the ratio of actual useful energy collectec 
to solar energy incident upon the collector and both use the same definition 
of collector area. However, the ASHRAE efficiency is determined from instan- 
taneous evaluation under tightly controlled, steady-state test conditions, 
while the operational collector efficiency is determined from the actual 
conditions of daily solar energy system operation. Measured monthly values of 
operational incident energy and computed values of operational collector 
efficiency are presented in Table 5-5. 

5.3.1.2 Storage 

Storage performance data for the Stewart-Teele-Mitchell site for the reporting 
period is shown in Table 5-6. Results of analysis of solar energy losses 
during transport and storage are shown in Table 5-7. This table contains an 
evaluation of solar energy transport losses as a fraction of energy trans- 
ported to subsystems. 



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5-13 



TABLE 5-7. SOLAR ENERGY LOSSES - STORAGE AND TRANSPORT 
STEWART-TEELE-MITCHELL 





MONTH TOTAL 




NOV 


DEC 


JAN 


FEB 


MAR 








1. SOLAR ENERGY (SE) COLLECTED 


















MINUS SE DIRECTLY TO LOADS 


1.77 


1.85 


0.61 


3.27 


3.90 






11.40 


(million Btu) 


















2. SE TO STORAGE 


1.60 


1.69 


0.58 


3.00 


3.43 






10.30 


(million Btu) 


















3. LOSS - COLLECTOR TO STORAGE (%) 


















1 -2 

1 


10 


9 


5 


8 


12 






10 


4. CHANGE IN STORED ENERGY 
(million Btu) 


0.08 


-0.07 


-0.13 


0.21 


-0.01 






0.10 


5. SOLAR ENERGY -STORAGE TO 


















DHW SUBSYSTEM (million Btu) 








0.20 


0.33 


0.49 






1.02 


6. SOLAR ENERGY -STORAGE TO 


















SPACE HEATING SUBSYSTEM 


0.56 


1.09 


0.13 


1.48 


1.95 






5.21 


(million Btu) 


















7. SOLAR ENERGY - STORAGE TO 


















SPACE COOLING SUBSYSTEM 


N.A. 


N.A. 


N.A. 


N.A. 


N.A. 






N.A. 


(million Btu) 


















8. LOSS FROM STORAGE (%) 
2 -(4 + 5+6+7) 
2 


60 


40 


66 


33 


29 






39 


9. HOT WATER SOLAR ENERGY (HWSE) 
FROM STORAGE (million Btu) 








0.20 


0.33 


0.49 






1.02 


10. LOSS - STORAGE TO HWSE (%) 
























5-9 
5 


















11. HEATING SOLAR ENERGY (HSE) 
FROM STORAGE 


0.36 


0.82 


0.11 


1.10 


1.39 






3.78 


(million Btu) 


















12. LOSS - STORAGE TO HSE (%) 


















6- 11 
6 


36 


25 


15 


26 


29 






27 



* - Denotes unavailable data 
N.A. - Denotes not applicable data 



S002 



5-14 



During the reporting period, total solar energy delivered to storage was 10.30 
million Btu. There were 6.23 million Btu delivered from storage to the 
DHW and space heating subsystems. Energy loss from storage was 3.99 million 
Btu. This loss represented 39 percent of the energy delivered to storage. 
The storage efficiency was 61 percent: This is calculated as the ratio of 
the sum of the energy removed from storage and the change in stored energy, 
to the energy delivered to storage. The average storage temperature for the 
period was 94°F. 

Storage subsystem performance is evaluated by comparison of energy to storage, 
energy from storage and the change in stored energy. The ratio of the sum of 
energy from storage and the change in stored energy, to the energy to storage 
is defined as storage efficiency, r\ . This relationship is expressed in the 
equation 

n s - (AQ + Q so )/Q si 



where: 

aQ = change in stored energy. This is the difference in 
the estimated stored energy during the specified 
reporting period, as indicated by the relative 
temperature of the storage medium (either positive 
or negative value) 



Q = energy from storage. This is the amount of energy 
extracted by the load subsystem from the primary 
storage medium 



Q .= energy to storage. This is the amount of energy 

(both solar and auxiliary) delivered to the primary 
storage medium 



5-15 



5.3.2 Domestic Hot Water (DHW) Subsystem 

The DHW subsystem performance for the Stewart-Teele-Mitchell site for the 
reporting period is shown in Table 5-8. The DHW subsystem consumed 1.02 
million Btu of solar energy and 2.51 million Btu of auxiliary electrical 
energy to satisfy a hot water load of 2.30 million Btu. The solar fraction 
of this load was 13 percent. 

The performance of the DHW subsystem is described by comparing the amount of 
solar energy supplied to the subsystem with the total energy required by the 
subsystem. The total energy required by the subsystem consists of both solar 
energy and auxiliary thermal energy. The DHW load is defined as the amount 
of energy required to raise the mass of water delivered by the DHW subsystem 
between the temperature at which it entered the subsystem and its delivery 
temperature. The DHW solar fraction is defined as the portion of the DHW 
load which is supported by solar energy. 

5.3.3 Space Heating Subsystem 

The space heating subsystem performance for the Stewart-Teele-Mitchell site 
for the reporting period is shown in Table 5-9. The space heating subsystem 
consumed 4.36 million Btu of solar energy and 69.17 million Btu of auxiliary 
fossil fuel energy to satisfy a space heating load of 49.10 million Btu. The 
solar fraction of this load was 9 percent. 

The performance of the space heating subsystem is described by comparing the 
amount of solar energy supplied to the subsystem with the energy required to 
satisfy the total space heating load. The energy required to satisfy the 
total load consists of both solar energy and auxiliary thermal energy. The 
ratio of solar energy supplied to the load to the total load is defined as 
the heating solar fraction. 



5-16 



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5-18 



5.4 Operating Energy 

Measured values of the Stewart-Teele-Mitchell solar energy system and sub- 
system operating energy for the reporting period are presented in Table 5-10. 
A total of 3.80 million Btu of operating energy was consumed by the entire 
system during the reporting period. 

Operating energy for a solar energy system is defined as the amount of elec- 
trical energy required to support the subsystems without affecting their 
thermal state. 

Total system operating energy for Stewart-Teele-Mitchell is the energy required 
to support the energy collection and storage subsystem (ECSS), the DHW sub- 
system and the space heating subsystem. With reference to the system sche- 
matic (Figure 3-1), the ECSS operating energy includes pumps PI (EP100) and 
P2 (EP200). One hundred percent of the operating energy of pumps PI and P2 
is assigned to the Ecss when the sytem is in the collector to storage mode 
and 75 percent is assigned when the system is in the collector to space heating 
mode. The DHW subsystem operating energy consists of pump P4 (EP300). The 
space heating subsystem operating energy consists of pump P3 (EP201, and 
blower (EP400). Additionally, 25 percent of the operating energy of pumps 
PI (EP100) and P2 (EP200) is assigned to the space heating subsystem when the 
system is in the collector-to-space heating mode. 

5.5 Energy Savings 

Energy savings for the Stewart-Teele-Mitchell site for the reporting period 
are presented in Table 5-11. For this period the total savings of electrical 
energy were 0.71 million Btu for a monthly average of 0.14 million Btu; total 
savings of fossil fuel energy were 7.25 million Btu, for a monthly average 
of 1.45 million Btu. An electrical energy expense of 0.99 million Btu was 
incurred during the reporting period for the operation of solar energy trans- 
portation pumps. 



5-19 



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5-21 



Solar energy system savings are realized whenever energy provided by the 
solar energy system is used to meet system demands which would otherwise be 
met by auxiliary energy sources. The operating energy required to provide 
solar energy to the load subsystems is subtracted from the solar energy 
contribution to determine net savings. 

The auxiliary source at Stewart-Teele-Mitchell consists of an oil-fired 
furnance for space heating and an electrical DHW heater. The units are 
considered to be 70 and 100 percent efficient for computational purposes. 



5-22 



6. REFERENCES 

1. U.S. Department of Energy, National Solar Data Network , prepared 
under contract number EG-77-C-4049 by IBM Corporation, 
December 1977. 

2. J. T. Smok, V. S. Sohoni , J. M. Nash, "Processing of Instrumented 
Data for the National Solar Heating and Cooling Demonstration 
Program," Conference on Performance Monitoring Techniques for 
Evaluation of Solar Heating and Cooling Systems, Washington, D.C., 
April 1978. 

3. E. Streed, et. al., Thermal Data Requirements and Performance 
Evaluation Procedures for the National Solar Heating and Cooling 
Demonstration Program , NBSIR-76-1137, National Bureau of Standards, 
Washington, D.C., 1976. 

4. Mears, J. C. Reference Monthly Environmental Data for Systems in 
the National Solar Data Network . Department of Energy report 
SOLAR/0019-79/36. Washington, D.C., 1979. 

5. ASHRAE Standard 93-77 , Methods of Testing to Determine the Thermal 
Performance of Solar Collectors , The American Society of Heating, 
Refrigeration and Air Conditioning Engineers, Inc., New York, N.Y., 
1977. 

6.# Monthly Performance Report , Stewart-Teele-Mitchell , SOLAR/1018-78/11, 
Department of Energy, Washington, D.C., (November 1978). 

7.# Monthly Performance Report , Stewart-Teele-Mitchell , SOLAR/1018-78/12, 
Department of Energy, Washington, D.C. , (December 1978). 

8.# Monthly Performance Report , Stewart-Teele-Mitchell , SOLAR/1018-79/01, 
Department of Energy, Washington, D.C, (January 1979). 

9.# Monthly Performance Report , Stewart-Teele-Mitchell , SOLAR/1018-79/02, 
Department of Energy, Washington, D.C, (February 1979). 

10. # Monthly Performance Report , Stewart-Teele-Mitchell , SOLAR/1018-79/03, 
Department of Energy, Washington, D.C, (March 1979). 



#Copies of these reports may be obtained from Technical Information Center, 
0. Box 62, Oak Ridge, Tennessee 37830. 



6-1 



APPENDIX A 
DEFINITIONS OF PERFORMANCE FACTORS AND SOLAR TERMS 



COLLECTOR ARRAY PERFORMANCE 

The collector array performance is characterized by the amount of solar 
energy collected with respect to the energy available to be collected. 

o INCIDENT SOLAR ENERGY (SEA) is the total insolation available 
on the gross collector array area. This is the area of the 
collector array energy-receiving aperture, including the 
framework which is an integral part of the collector structure. 

o OPERATIONAL INCIDENT ENERGY (SEOP) is the amount of solar energy 
incident on the collector array during the time that the col- 
lector loop is active (attempting to collect energy). 

o COLLECTED SOLAR ENERGY (SECA) is the thermal energy removed 
from the collector array by the energy transport medium. 

o COLLECTOR ARRAY EFFICIENCY (CAREF) is the ratio of the energy 
collected to the total solar energy incident on the collector 
array. It should be emphasized that this efficiency factor is 
for the collector array, and available energy includes the 
energy incident on the array when the collector loop is inac- 
tive. This efficiency must not be confused with the more 
common collector efficiency figures which are determined from 
instantaneous test data obtained during steady-state operation 
of a single collector unit. These efficiency figures are often 
provided by collector manufacturers or presented in technical 
journals to characterize the functional capability of a partic- 
ular collector design. In general, the collector panel maximum 
efficiency factor will be significantly higher than the col- 
lector array efficiency reported here. 

STORAGE PERFORMANCE 

The storage performance is characterized by the relationships among the 
energy delivered to storage, removed from storage, and the subsequent 
change in the amount of stored energy. 

o ENERGY TO STORAGE (STEI) is the amount of energy, both solar 
and auxiliary, delivered to the primary storage medium. 

o ENERGY FROM STORAGE (STEO) is the amount of energy extracted 
by the load subsystems from the primary storage medium. 



A-l 



o CHANGE IN STORED F.NERGY (STECH) is the difference in the estimated 

stored energy during the specified reporting period, as indicated 

by the relative temperature of the storage medium (either posi- 
tive or negative value). 

o STORAGE AVERAGE TEMPERATURE (TST) is the mass-weighted average 
temperature of the primary storage medium. 

o STORAGE EFFICIENCY (STEFF) is the ratio of the sum of the energy 
removed from storage and the change in stored energy to the 
energy delivered to storage. 

ENERGY COLLECTION AND STORAGE SUBSYSTEM 

TJie Energy Collection and Storage Subsystem (ECSS) is composed of the 
collector array, the primary storage medium, the transport loops between 
these, and other components in the system design which are necessary to 
mechanize the collector and storage equipment. 

o INCIDENT SOLAR ENL'RGY (SEA) is the total insolation available 
on the gross collector array area. This is the area of the 
collector array energy- receiving aperture, including the frame- 
work which is an integral part of the collector structure. 

o AMBIENT TEMPERATUR E (TA) is the average temperature of the out- 
door environment at the site. 

o ENERGY TO LOADS (SEL) is the total thermal energy transported 
from the ECSS to all load subsystems. 

o AUXILIARY THERMAL ENERGY TO ECSS (CSAUX) is the total auxiliary 
energy supplied to the ECSS, including auxiliary energy added to 
the storage tank, heating devices on the collectors for freeze- 
protection, etc. 

o ECSS OPERATING ENERGY (CSOPE) is the critical operating energy 
required to support the ECSS heat transfer loops. 

HOT WATER SUBSYSTEM 

The hot water subsystem is characterized by a complete accounting of the 
energy flow into and from the subsystem, as well as an accounting of 
internal energy. The energy into the subsystem is composed of auxiliary 
fossil fuel, and electrical auxiliary thermal energy, and the operating 
energy for the subsystem. 

o HOT WATER LOAD (HWL) is the amount of energy required to heat 
the amount of hot water demanded at the site from the incoming 
temperature to the desired outlet temperature. 



A-2 



o SOLAR FRACTION OF LOAD (HWSFR) is the percentage of the load 
demand which is supported by solar energy. 

o SOLAR ENERGY USE D (HWSE) is the amount of solar energy supplied 
to the hot water subsystem. 

o OPERATING ENERGY (HWOPE) is the amount of electrical energy 
required to support the subsystem, (e.g., fans, pumps, etc.) 
and which is not intended to directly affect the thermal state 
of the subsystem. 

o AUXILIARY THERMAL USED (HWAT) is the amount of energy supplied 
to the major components of the subsystem in the form of thermal 
energy in a heat transfer fluid, or its equivalent. This term 
also includes the converted electrical and fossil fuel energy 
supplied to the subsystem. 

o AUXILIARY FOSSIL FUEL (HWAF) is the amount of fossil fuel energy 
supplied directly to the subsystem. 

o ELECTRICAL ENERGY SAVINGS (HWSVE) is the estimated difference 
between the electrical energy requirements of an alternative 
conventional system (carrying the full load) and the actual 
electrical energy required by the subsystem. 

o FOSSIL FUEL SAVINGS (HWSVF) is the estimated difference between 
the fossil fuel energy requirements of the alternative conven- 
tional system (carrying the full load) and the actual fossil 
fuel energy requirements of the subsystem. 

SPACE HEATING SUBSYSTEM 

The space heating subsystem is characterized by performance factors account- 
ing for the complete energy flow into the subsystem. The average building 
temperature is tabulated to indicate the relative performance of the 
subsystem in satisfying the space heating load and in controlling the tem- 
perature of the conditioned space. 

o SPACE HEATING LOAD (HL) is the sensible energy added to the 
air in the building. 

o SOLAR FRACTION OF LOAD (HSFR) is the fraction of the sensible 
energy added to the air in the building derived from the solar 
energy system. 

o SOLAR ENERGY USED (HSE) is the amount of solar energy supplied 
to the space heating subsystem. 



A- 3 



OPERATING ENERGY (HOPE) is the amount of electrical energy 
required to support the subsystem, (e.g., fans, pumps, etc.) 
and which is not intended to directly affect the thermal state 
of the system. 

AUXILIARY THERMAL USED (HAT) is the amount of energy supplied 
to the major components of the subsystem in the form of thermal 
energy in a heat transfer fluid or its equivalent. This term 
also includes the converted electrical and fossil fuel energy 
supplied to the subsystem. 

AUXILIARY ELECTRICAL FUEL (HAE) is the amount of electrical 
energy supplied directly to the subsystem. 

ELECTRICAL ENERGY SAVINGS (HSVE) is the estimated difference 
between the electrical energy requirements of an alternative 
conventional system (carrying the full load) and the actual 
electrical energy required by the subsystem. 

BUILDING TEMPERATURE (TB) is the average heated space dry bulb 
temperature. 



A-4 



APPENDIX B 
SOLAR ENERGY SYSTEM PERFORMANCE EQUATIONS 
STEWART-TEELE-MITCHELL 



INTRODUCTION 

Solar energy system performance is evaluated by performing energy balance 
calculations on the system and its major subsystems. These calculations 
are based on physical measurement data taken from each sensor every 
320 seconds. This data is then mathematically combined to determine the 
hourly, daily, and monthly performance of the system. This appendix 
describes the general computational methods and the specific energy 
balance equations used for this site. 

Data samples from the system measurements are integrated to provide 
discrete approximations of the continuous functions which characterize 
the system's dynamic behavior. This integration is performed by summation 
of the product of the measured rate of the appropriate performance para- 
meters and the sampling interval over the total time period of interest. 

There are several general forms of integration equations which are 
applied to each site. These general forms are exemplified as follows: 
The total solar energy available to the collector array is given by 

-SOLAR ENERGY AVAILABLE = (1/60) S [1001 x AREA] x At 

where 1001 is the solar radiation measurement provided by the pyranometer 
in Btu per square foot per hour, AREA is the area of the collector array 
in square feet, Ax is the sampling interval in minutes, and the factor 
(1/60) is included to correct the solar radiation "rate" to the proper 
units of time. 

Similarly, the energy flow within a system is given typically by 

COLLECTED SOLAR ENERGY = l [M100 x AH] x At 

where M100 is the mass flow rate of the heat transfer fluid in lb /min and 
AH is the enthalpy change, in Btu/lb , of the fluid as it passes through 
the heat exchanging component. 

For a liquid system AH is generally given by 

AH = C AT 

where C is the average specific heat, in Btu/(lb -°F), of the heat trans- 
fer fluid and AT, in °F, is the temperature differential across the heat 
exchanging component. 



B-l 



For an air system AH is generally given by 

iH ■ H a< T out> " H a< T in> 

where H (T) is the enthalpy, in Btu/lb , of the transport air evaluated 
at the inlet and outlet temperatures or the heat exchanging component. 

H (T) can have various forms, depending on whether or not the humidity 
rcltio of the transport air remains constant as it passes through the heat 
exchanging component. 

For electrical power, a general example is 

ECSS OPERATING ENERGY = (3413/60) E [EP100] x At 

where EP100 is the power required by electrical equipment in kilowatts 
and the two factors (1/60) and 3413 correct the data to Btu/min. 

These equations are comparable to those specified in "Thermal Data 
Requirements and Performance Evaluation Procedures for the National Solar 
Heating and Cooling Demonstration Program." This document was prepared 
by an interagency committee of the Government, and presents guidelines 
for thermal performance evaluation. 

Performance factors are computed for each hour of the day. Each integra- 
tion process, therfore, is performed over a period of one hour. Since 
long-term performance data is desired, it is necessary to build these 
houHy performance factors to daily values. This is accomplished, for 
energy parameters, by summing the 24 hourly values. For temperatures, 
the hourly values are averaged. Certain special factors, such as effi- 
ciencies, require appropriate handling to properly weight each hourly 
sample for the daily value computation. Similar procedures are required 
to convert daily values to monthly values. 



B-2 



EQUATIONS USED TO GENERATE MONTHLY PERFORMANCE VALUES 

NOTE: SENSOR IDENTIFICATION (MEASUREMENT) NUMBERS REFERENCE SYSTEM 
SCHEMATIC FIGURE 3-1 



AVERAGE AMBIENT TEMPERATURE (°F) 

TA = (1/60) x I T001 x At 
AVERAGE BUILDING TEMPERATURE (°F) 

TB = (1/60) x Z T600 x At 
DAYTIME AVERAGE AMBIENT TEMPERATURE (°F) 

TDA = (1/360) x Z T001 x Ax 

FOR + 3 HOURS FROM SOLAR NOON 
INCIDENT SOLAR ENERGY PER SQUARE FOOT (BTU/FT 2 ) 

SE = (1/60) x Z 1001 x At 
OPERATION INCIDENT SOLAR ENERGY (BTU) 

SEOP = (1/60) x Z [1001 x CLAREA] x Ax 
WHEN THE COLLECTOR LOOP IS ACTIVE 

HUMIDITY RATIO FUNCTION (BTU/lb - °F) 

m ' 

HRF = 0.24 + 0.44 x HR 

WHERE 0.24 IS THE SPECIFIC HEAT AND HR IS THE HUMIDITY RATIO OF THE 
TRANSPORT AIR. THIS FUNCTION IS USED WHENEVER THE HUMIDITY RATIO 
WILL REMAIN CONSTANT AS THE TRANSPORT AIR FLOWS THROUGH A HEAT 
EXCHANGING DEVICE. 

COLLECTED SOLAR ENERGY (BTU/FT 2 ) 

SEC - SECA/CLAREA 
ECSS OPERATING ENERGY (BTU) 

CSOPE = CS0PE1 + CS0PE2 

WHERE CS0PE1 = 56.8833 x Z (EP100 + EP200) x At 

WHEN SYSTEM IS IN THE COLLECTOR-TO-STORAGE MODE AND 
CS0PE2 = 56.8833 x 0.75 x Z (EP100 + EP200) x Ax 

WHEN SYSTEM IS IN THE COLLECTOR-TO-SPACE HEATING MODE 



B-3 



ECSS SOLAR CONVERSION EFFICIENCY 

CSCEF = CSEO/SEA 
COLLECTOR ARRAY EFFICIENCY 

CAREF = SECA/SEA 
SOLAR ENERGY COLLECTED BY THE ARRAY (BTU) 

SECA = Z [Ml 00 x CP17 (T100 + T150)/2 x (T150 - T100)] x At 

WHERE CP17 IDENTIFIES THE SPECIFIC HEAT OF THE 40% BY VOLUME 
SOLUTION OF ETHYLENE-GLYCOL IN WATER USED AS THE HEAT TRANSFER 
MEDIUM 

SOLAR ENERGY TO STORAGE (BTU) 

STEI = E [M200 x HWD (T251 , T201)] x Ax 
SOLAR ENERGY FROM STORAGE (BTU) 

STEO = STEOHC + HWSE 

WHERE STEOHC = Z [M200 x HWD (T251 , T201)] x At 

WHEN SYSTEM IS IN THE STORAGE-TO-SPACE HEATING MODE 
AVERAGE TEMPERATURE OF STORAGE (BTU) 

TST = (1/60) x Z [(T202 + T203 + T204)/3] x At 
CHANGE IN STORED ENERGY (BTU) 

STECH = STOCAP x (STECH1 - STECH1 ) 

WHERE THE SUBSCRIPT REFERS TO A PRIOR REFERENCE VALUE 

P 

STORAGE EFFICIENCY 

STEFF = (STECH + STEO)/STEI 
SPACE HEATING SUBSYSTEM OPERATING ENERGY (BTU) 
HOPE = H0PE1 + H0PE2 + H0PE3 

WHERE H0PE1 = 56.8833 x E EP201 x At 

WHEN SYSTEM IS IN THE STORAGE-TO-SPACE HEATING MODE 



B-4 



H0PE2 = 56.8833 x 0.25 x I (EP10Q + EP200) x Ax 

WHEN SYSTEM IS IN THE COLLECTOR-TO-SPACE HEATING MODE 

H0PE3 = 56.8833 x E EP400 x Ax 

ENERGY DELIVERED FROM ECSS TO LOAD (BTU) 

CSEO = STEO + HSE2 

WHERE HSE2 IS THE ENERGY DELIVERED TO THE SPACE HEATING LOAD WHEN 
THE SYSTEM IS IN THE COLLECTOR-TO-SPACE HEATING MODE 

SOLAR ENERGY TO SPACE HEATING SUBSYSTEM (BTU) 

HSE = HSE1 + HSE2 

WHERE HSE1 = E [M201 x HWD (T400, T450)] x Ax 

WHEN SYSTEM IS IN THE STORAGE-TO-SPACE HEATING MODE 
HSE2 = E [M204 x HWD (T400, T450)] x Ax 

WHEN THE SYSTEM IS IN THE COLLECTOR-TO-SPACE HEATING MODE 
SPACE HEATING SUBSYSTEM LOAD (BTU) 

HL = HAT + HSE 
SPACE HEATING SUBSYSTEM AUXILIARY THERMAL ENERGY (BTU) 

HAT = 140,000 x 0.7 x (1/60) E F400 x Ax 
SPACE HEATING SUBSYSTEM AUXILIARY FOSSIL FUEL ENERGY (BTU) 

HAF = HAT/0.7 
SPACE HEATING SUBSYSTEM ELECTRICAL ENERGY SAVINGS (BTU) 

HSVE = - (H0PE1 + H0PE2) 
SPACE HEATING SUBSYSTEM FOSSIL FUEL ENERGY SAVINGS (BTU) 

HSVF = HSE/0.6 
SPACE HEATING SUBSYSTEM SOLAR FRACTION (PERCENT) 

HSFR = 100 x HSE/HL 
SOLAR ENERGY TO DHW SUBSYSTEM (BTU) 

HWSE = E [M300 x HWD (T300, T350)] x Ax 



B-5 



DHW SUBSYSTEM LOAD (BTU) 

HWL = E [M301 x HWD (T352, T301)] x At 
DHW SUBSYSTEM OPERATING ENERGY (BTU) 

HWOPE = 56.8833 x E EP300 x At 
DHW SUBSYSTEM AUXILIARY FUEL ENERGY (BTU) 

HWAE = 56.8833 x E EP301 x At 
DHW SUBSYSTEM AUXILIARY THERMAL ENERGY (BTU) 

HWAT = HWAE 
DHW SUBSYSTEM SOLAR FRACTION (PERCENT) 

HWSFR = 100 x HWTKSE/(HWTKSE + HWTKAUX) 

WHERE HWTKSE IS THE ENERGY IN THE DHW TANK ATTRIBUTABLE TO SOLAR 
AND HWTKAUX IS THE ENERGY IN THE DHW TANK ATTRIBUTABLE TO AUXILIARY 
AT ANY GIVEN TIME 

DHW SUBSYSTEM ELECTRICAL ENERGY SAVINGS (BTU) 

HWSVE = E [M301 x (T351, T301)] x At - HWOPE 

SERVICE SUPPLY WATER TEMPERATURE (°F) 

TSW = (1/60) x E T301 x At 

WHEN WATER IS BEING DRAWN 

SERVICE HOT WATER TEMPERATURE (°F) 

THW = (1/60) x E T352 x At 

WHEN WATER IS BEING DRAWN 

HOT WATER CONSUMED (GALLONS) 

HWCSM = W301 

WHERE W301 IS A TOTALIZING WATER METER WITH RANGE TO 100 GALLONS 

TOTAL ENERGY CONSUMED (BTU) 

TE^SM = SYSOPE + AXE + SECA + AXF 



B-6 



SYSTEM OPERATING ENERGY (BTU) 

SYSOPE = HOPE + CSOPE + HWOPE 
SYSTEM LOAD (BTU) 

SYSL = HWL + HL 
SOLAR ENERGY TO LOAD SUBSYSTEMS (BTU) 

SEL = HWSE + HSE 
SOLAR FRACTION OF SYSTEM LOAD 

SFR = (HWSFR x HWL + HSFR x HL)/SYSL 
AUXILIARY THERMAL ENERGY TO LOADS (BTU) 

AXT = HWAT + HAT 
AUXILIARY ELECTRICAL ENERGY TO LOADS (BTU) 

AXE = HWAE 
AUXILIARY FOSSIL FUEL ENERGY TO LOADS (BTU) 

AXF '= HAF 
TOTAL ELECTRICAL ENERGY SAVINGS 

TSVE = HWSVE + HSVE - CSOPE 
TOTAL FOSSIL FUEL ENERGY SAVINGS 

TSVF = HSVF 
SYSTEM PERFORMANCE FACTOR 

SYSPF = SYSL/[AXF + 3.33 x (AXE + SYSOPE)] 



B-7 



APPENDIX C 
LONG-TERM AVERAGE WEATHER CONDITIONS 



This appendix contains a table which lists the long-term average weather 
conditions for each month of the year for this site. 



C-l 



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C-2 



APPENDIX D 
MONTHLY SOLAR ENERGY DISTRIBUTION FLOWCHARTS 



The flowcharts in this appendix depict the quantity of solar energy corre- 
sponding to each major component or characteristic of the Stewart-Teele 
Mitchell solar energy system for five months of the reporting period. Each 
monthly flowchart represents a solar energy balance as the total input equals 
the total output. 






D-l 



FIGURE D-l. SOLAR ENERGY (MILLION BTU) DISTRIBUTION FLOWCHART 

STEWART-TEELE-MITCHELL 



NOVEMBER 1978 



Incident 
Solar Energy 






Solar Energy 
Storage Losses 


11.49 








0.96 




i 






in 






Change in 
Stored Energy 




i 


Operational 
Incident 
Solar Energy 




Transport Loss 
Collector to 
Storage 


ECSS Subsystem 
Operating Energy 












0.08 










6.58 


0.17 


0.08 




* 






1 
















i 
I 






Collected 
Solar Energy 








Solar Energy 
to Storage 


i 


Solar Energy 
from Storage 










1.86 






in 


1.60 








0.56 








Transport Loss 
Collector to DHW 








Transport Loss 
Storage to DHW 


















N.A. 























Domestic Hot 
Water Solar 
Energy Used 


























N.A. 









DHW Subsystem 
Operating Energy 




Domestic Hot 
Water Auxiliary 
Thermal Used 









0.26 










Domestic Hot 
Water Load 










(D 




0.02 






in 








Transport Loss 
Collector to 
Space Heating 








Transport Loss 
Storage to 
Space Heating 

























0.20 














Space Heating 
Solar Energy Used 


























0.09 


0.36 






Space Heating 
Subsystem 
Operating Energy 




Space Heating 
Auxiliary Thermal 
Used 






0.90 


4.70 










Space Heating 
Load 










d) 




5.15 














Transport Loss 
Collector to 
Space Cooling 








Transport Loss 
Storage to 
Space Cooling 


















N.A. 








N.A. 














Space Cooling 
Solar Energy Used 


























N.A. 


N.A. 






Space Cooling 
Subsystem 
Operating Energy 




Space Cooling 
Auxiliary Thermal 
Used 










d) 


N.A. 


N.A. 














Total Loss - 
Collector to 
Storage and Loads 






Space Cooling 
Load 




Total Loss - 
Storage to Loads 


















0.17 


N.A. 


0.20 





(li 



* Denotes Unavailable Data 

N.A. denotes not applicable data 

(1) May contribute to offset of space heating Ipad (if known - see text for discussion) 

D-2 



$002 



FIGURE D-2. SOLAR ENERGY (MILLION BTU) DISTRIBUTION FLOWCHART - DECEMBER 1978 

STEWART-TEELE-MITCHELL 



Incident 
Solar Energy 






Solar Energy 
Storage Losses 


( 


9.26 








0.67 






1 






id 






Change in 
Stored Energy 




i 






Operational 
Incident 
Solar Energy 




Transport Loss 
Collector to 
Storage 


ECSS Subsystem 
Operating Energy 












-0.07 




6.44 






0.16 


0.08 




♦ 
























i 

1 








Collected 
Solar Energy 








Solar Energy 
to Storage 


i 


Solar Energy 
from Storage 














2.03 






in 


1.69 






id 


1.09 










Transport Loss 
Collector to DHW 








Transport Loss 
Storage to DHW 




















N.A. 























— 


Domestic Hot 
Water Solar 
Energy Used 






















N.A. 









DHW Subsystem 
Operating Energy 




Domestic Hot 
Water Auxiliary 
Thermal Used 






Q 


0.73 










Domestic Hot 
Water Load 










(it 




0.55 






id 








Transport Loss 
Collector to 
Space Heating 








Transport Loss 
Storage to 
Space Heating 

























Q.27 














Space Heating 
Solar Energy Used 


























0.18 


0.82 






Space Heating 
Subsystem 
Operating Energy 




Space Heating 
Auxiliary Thermal 
Used 






0.63 


8.81 










Space Heating 
Load 










(D 




9.82 














Transport Loss 
Collector to 
Space Cooling 








Transport Loss 
Storage to 
Space Cooling 


















N.A. 








N.A. 














Space Cooling 
Solar Energy Used 


























N.A. 


N.A. 






Space Cooling 
Subsystem 
Operating Energy 




Space Cooling 
Auxiliary Thermal 
Used 










(D 


N.A. 


N.A. 














Total Loss - 
Collector to 
Storage and Loads 






Space Cooling 
Load 




Total Loss - 
Storage to Loads 


















0.16 


N.A. 


0.27 





* Denotes Unavailable Data 

N.A. denotes not applicable data 

(1) May contribute to offset of space heating l^ad (if known - see text for discussion) 

D-3 



SO02 



FIGURE D-3. 



SOLAR ENERGY (MILLION BTU) DISTRIBUTION FLOWCHART - JANUARY 1979 

STEWART-TEELE-MITCHELL 



Incident 
Solar Energy 






Solar Energy 
Storage Losses 


6.07 








0.38 


1 








m 






Change in 
Stored Energy 








Operational 
Incident 
Solar Energy 




Transport Loss 
Collector to 
Storage 


ECSS Subsystem 
Operating Energy 












-0.13 










2.40 


0.03 


0.04 




♦ 






1 
















i 
I 






Collected 
Solar Energy 








Solar Energy 
to Storage 


i 
1 


Solar Energy 
from Storage 










0.63 






id 


0.58 








0.33 








Transport Loss 
Collector to DHW 








Transport Loss 
Storage to DHW 


















N.A. 























Domestic Hot 
Water Solar 
Energy Used 


























N.A. 


0.20 






DHW Subsystem 
Operating Energy 




Domestic Hot 
Water Auxiliary 
Thermal Used 






0.08 


0.60 










Domestic Hot 
Water Load 










(D 




0.59 






(1) 








Transport Loss 
Collector to 
Space Heating 








Transport Loss 
Storage to 
Space Heating 























0.02 














Space Heating 
Solar Energy Used 


























0.02 


0.11 






Space Heating 
Subsystem 
Operating Energy 




Space Heating 
Auxiliary Thermal 
Used 






0.61 


16.25 










Space Heating 
Load 










id 




16.38 














Transport Loss 
Collector to 
Space Cooling 








Transport Loss 
Storage to 
Space Cooling 


















N.A. 








N.A. 














Space Cooling 
Solar Energy Used 


























N.A. 


N.A. 






Space Cooling 
Subsystem 
Operating Energy 




Space Cooling 
Auxiliary Thermal 
Used 










in 


N.A. 


N.A. 














Total Loss - 
Collector to 
Storage and Loads 






Space Cooling 
Load 




Total Loss - 
Storage to Loads 


















a. 03 


N.A. 


0.0? 





111 



* Denotes Unavailable Data 

N.A. denotes not applicable data 

(1) May contribute to offset of space heating \pad (if known - see text for discussion) 

D-4 



■008 



FIGURE D-4. SOLAR ENERGY (MILLION BTU) DISTRIBUTION FLOWCHART 

STEWART-TEELE-MITCHELL 



FEBRUARY 1979 



Incident 
Solar Energy 








Solar Energy 
Storage Losses 


17.96 






0.98 


1 


' 






in 






Change in 
Stored Energy 


i 




Operational 
Incident 
Solar Energy 




Transport Loss 
Collector to 
Storage 


ECSS Subsystem 
Operating Energy 










0.21 










13.56 


0.27 


0.13 




♦ 






















i 
1 




Collected 
Solar Energy 








Solar Energy 
to Storage 


• 


Solar Energy 
from Storage 










in 


3.48 






id 


3.00 






1.81 








Transport Loss 
Collector to DHW 








Transport Loss 
Storage to DHW 


















N.A. 























Domestic Hot 
Water Solar 
Energy Used 
















in 










N.A. 


0.33 






DHW Subsystem 
Operating Energy 




Domestic Hot 
Water Auxiliary 
Thermal Used 






0.06 


0.47 










Domestic Hot 
Water Load 










in 




Q.52 












Transport Loss 
Collector to 
Space Heating 








Transport Loss 
Storage to 
Space Heating 

























0.38 














Space Heating 
Solar Energy Used 


























0.21 


1.10 






Space Heating 
Subsystem 
Operating Energy 




Space Heating 
Auxiliary Thermal 
Used 






0.62 


8.55 










Space Heating 
Load 










(i) 




9.86 












Transport Loss 
Collector to 
Space Cooling 








Transport Loss 
Storage to 
Space Cooling 
















N.A. 








N.A. 














Space Cooling 
Solar Energy Used 












■^^ 














N.A. 


N.A. 






Space Cooling 
Subsystem 
Operating Energy 




Space Cooling 
Auxiliary Thermal 
Used 










(ii 


N.A. 


N.A. 












Total Loss - 
Collector to 
Storage and Loads 






Space Cooling 
Load 




Total Loss - 
Storage to Loads 






• 












0.27 


N.A. 


Q.38 





(1) 



* Denotes Unavailable Data 

N.A. denotes not applicable data 

(1) May contribute to offset of space heating \pad (if known - see text for discussion) 

D-5 



S002 



FIGURE D-5. SOLAR ENERGY (MILLION BTU) DISTRIBUTION FLOWCHART - MARCH 1979 

STEWART-TEELE-MITCHELL 



Incident 
Solar Energy 






Solar Energy 
Storage Losses 


15.57 








1.00 




1 






(D 






Change in 
Stored Energy 








Operational 
Incident 
Solar Energy 




Transport Loss 
Collector to 
Storage 


ECSS Subsystem 
Operating Energy 












0.01 










11.72 


0.47 


0.15 




* 






1 
















i 
I 






Collected 
Solar Energy 








Solar Energy 
to Storage 


i 
1 


Solar Energy 
from Storage 










3.98 






d) 


3.43 








2.44 








Transport Loss 
Collector to DHW 








Transport Loss 
Storage to DHW 


















N.A. 








0. 














Domestic Hot 
Water Solar 
Energy Used 


























N.A. 


0.49 






DHW Subsystem 
Operating Energy 




Domestic Hot 
Water Auxiliary 
Thermal Used 






0.07 


0.45 










Domestic Hot 
Water Load 










d) 




0.62 






til 








Transport Loss 
Collector to 
Space Heating 








Transport Loss 
Storage to 
Space Heating 

























0.56 














Space Heating 
Solar Energy Used 


























Q.08 


1.39 






Space Heating 
Subsystem 
Operating Energy 




Space Heating 
Auxiliary Thermal 
Used 






0.36 


6.43 










Space Heating 
Load 










<i> 




7.89 














Transport Loss 
Collector to 
Space Cooling 








Transport Loss 
Storage to 
Space Cooling 


















N.A. 








N.A. 














Space Cooling 
Solar Energy Used 


























N.A. 


N.A. 






Space Cooling 
Subsystem 
Operating Energy 




Space Cooling 
Auxiliary Thermal 
Used 










(i) 


N.A. 


N.A. 














Total Low - 
Collector to 
Storage and Loads 






Space Cooling 
Load 




Total Loss - 
Storage to Loads 


















0.47 


N.A- 


0.56 





* Denotes Unavailable Data 

N.A. denote* not applicable data 

(1) May contribute to offset of space heating load (if known - see text for discussion) 

D-6 



MM 



APPENDIX E 
MONTHLY SOLAR ENERGY DISTRIBUTIONS 



The data tables provided in this appendix present an indication of solar 
energy distribution, intentional and unintentional, in the Stewart-Teele 
Mitchell solar energy system. Tables are provided for five months of the 
reporting period. 



E-l 



_0 

% 



TABLE E-l. SOLAR ENERGY DISTRIBUTION - NOVEMBER 1978 

STEWART-TEELE-MITCHELL 

1 .86 mi 1 1 ion Btu 
100% OT:U T0TAL SOLAR ENERGY COLLECTED 

_0^_ million Btu S0LAR ENERGy TQ LQADS 

million Btu SQLAR ENERGY T0 DH w SUBSYSTEM 

°24 5 % mi11l °" BtU SOLAR ENERGY TO SPACE HEATING SUBSYSTEM 

N A 
— U_ million Btu $0LAR ENERGY T0 spACE C00LING SUBSYSTEM 

' y mi11lon Btu SOLAR ENERGY LOSSES 

_0J£_ million Btu $0LAR ENERGY L0SS FR0M STORAGE 

DC 7o 

°20 7 % mil1l ° n BtU SOLAR ENERGY LOSS IN TRANSPORT 
JLW_ million Btu C0LLECT0R TQ ST0RAGE L0SS 

*_ million Btu COLLECTOR T0 L0AD LQSS 

N.A. million Btu CQLLECT0R T0 DHW LQSS 



_JL_ million Btu COLLECTOR TQ $pACE HEATING 4.0SS 
N.A. million Btu 



% 
0.20 million Btu 



11 % 

* million Btu 

% 

0.20 million Btu 



11 % 
N.A. million Btu 



COLLECTOR TO SPACE COOLING LOSS 
STORAGE TO LOAD LOSS 

STORAGE TO DHW LOSS 

STORAGE TO SPACE HEATING LOSS 

STORAGE TO SPACE COOLING LOSS 



_0 1 0^ million Btu s0| _ AR ENERGy ST0RAGE CHANGE 
* - Denotes unavailable data E-2 



TABLE E-2. SOLAR ENERGY DISTRIBUTION - DECEMBER 1978 

STEWART-TEELE-MITCHELL 

_L03_ million Btu T(JTAL $()LAR ENERGy C0LLECTED 
_KOO_ million Btu SQLAR ENERGy TQ L0ADS 

0_ million Btu S0| _ AR ENERGY T0 DHW SUBSYSTEM 

_^00_ million Btu s0| _ AR ENERGY T0 SPACE HEATING SUBSYSTEM 
N.A. million Btu $0LAR ENERGY T0 SPACE COOLING SUBSYSTEM 
_J^10 million Btu S0LAR ENERGy L0S$ES 

_0^67_ million Btu $0LAR ENERGY L0SS FROM STORAGE 
_0^43_ million Btu SQLAR ENERGY L0SS IN TRANS P0RT 
U6_ million Btu C0L| _ ECT0R TQ ST0RAGE L0SS 
nil ion Btu COLLECTOR TQ LQAD LQSS 
N.A. million Btu COLLECTOR JQ Dm LQSS 

lo 

nl lion Btu COL| _ ECTOR TQ SpACE HEATING L0SS 



0. 

* m" 

% 



* mi 

% 



% 
N.A. million Btu C0LLECT0R TQ $pACE C00LING L0SS 

10 

CL27^ million Btu ST0RAGE T0 LQAD L0S$ 

— * million Btu $T0RAGE TQ m LQSS 

10 

_0^27_ million Btu ST0RAGE TQ SpACE HEATING L0SS 
N.A. million Btu STQRAGE TQ $pACE C00LING L0SS 

10 



ill ion Btu S0| _ AR ENERGy STORAGE CHANGE 



=3% 
* - Denotes unavailable data E-3 



TABLE E-3. SOLAR ENERGY DISTRIBUTION - JANUARY 1979 

STEWART-TEELE-MITCHELL 

0.63 million Btu T0TAL SQLAR ENERGy C0L[ _ ECTED 



100% 

0.33 mi' ion Btu 



53% 



SOLAR ENERGY TO LOADS 



ill ion Btu SQLAR ENERGY T0 D HW SUBSYSTEM 



32°^ 



_qj^_ million Btu SQLAR ENERGY T0 SPACE HEATING SUBSYSTEM 
21 /o 

lion Btu $0LAR ENERGY TQ SPACE COOLING SUBSYSTEM 



% 
0-43 million Btu 



68 % 

0.38 mi" 

60% 



SOLAR ENERGY LOSSES 

SOLAR ENERGY LOSS FROM STORAGE 



SL$^. million Btu SQLAR ENERGY L0SS IN TRANSPORT 
8 * 

0.03 minion Btu COLLECTOR TQ STQRAGE lQ$s 



5 % 

* million Btu 



% 

N.A. million Btu 

% 

million Btu 



% 
N.A. million Btu 



COLLECTOR TO LOAD LOSS 

COLLECTOR TO DHW LOSS 
COLLECTOR TO SPACE HEATING LOSS 



% 
0.02 million Btu 



COLLECTOR TO SPACE COOLING LOSS 

n R + n 

STORAGE TO LOAD LOSS 



3 % 

* mi" ion Btu 



% 



STORAGE TO DHW LOSS 



0.02 million Btu $T0RAGE TQ spACE HEATING L0S s 
3 lo 

N.A. million Btu ST0RAGE TQ SpACE C00LING L0SS 

To 



lion Btu $0LAR ENERGY ST oRAGE CHANGE 



-21% 



* - Denotes unavailable data E-4 

N A _ flonntoc nnt annlirahlo An*--% 



TABLE E-4. SOLAR ENERGY DISTRIBUTION- FEBRUARY 1979 

STEWART-TEELE-MITCHELL 

_3^| million Btu T0TAL SQLAR ENERGy C0LLECTED 
1.64 million Btu $0LAR ENERGY TQ LQADS 



47% 

0.33 million Btu 

9 % 

1 .31 million Btu 
38% 

N.A. mil ion Btu 



SOLAR ENERGY TO DHW SUBSYSTEM 

SOLAR ENERGY TO SPACE HEATING SUBSYSTEM 

SOLAR ENERGY TO SPACE COOLING SUBSYSTEM 



million Btu SQLAR ENERQY LQSSES 



47 % 

0.98 mil 
28 % 

Q.65 million Btu 



19 % 

0.27 million Btu 
8 % 

* million Btu 



% 
0.38 million Btu 



SOLAR ENERGY LOSS FROM STORAGE 
SOLAR ENERGY LOSS IN TRANSPORT 

COLLECTOR TO STORAGE LOSS 
COLLECTOR TO LOAD LOSS 

COLLECTOR TO DHW LOSS 
COLLECTOR TO SPACE HEATING LOSS 
COLLECTOR TO SPACE COOLING LOSS 
[ TO LOAD LOSS 
STORAGE TO DHW LOSS 



% 

N.A. million Btu 

% 

* million Btu 



% 
N -A. million Btu 



11% 

* million Btu 



% 
38 million Btu ST0RAGE TQ $pACE HEATING L0SS 

11 lo 

jj^ml^on Btu STQRAGE TQ SpACE C00LING L0SS 

lo 



ill ion Btu SQLAR E( ^ ERGY ST0RAGE CHANGE 



6 % 
* - Dpnntp<; unavailable c\a \t\ 



TABLE E-5. SOLAR ENERGY DISTRIBUTION ■- MARCH 1979 

STEWART-TEELE-MITCHELL 

3.98 million Btu T0TAL SQLAR ENERGy C0LLECTED 



100% 

1.96 mi 

49 % 

0.49 million Btu 



12 % 
1 .47 million Btu 



37 % 
N.A. million Btu 



SOLAR ENERGY TO LOADS 

SOLAR ENERGY TO DHW SUBSYSTEM 

SOLAR ENERGY TO SPACE HEATING SUBSYSTEM 

SOLAR ENERGY TO SPACE COOLING SUBSYSTEM 



^03_ million Btu S0LAR ENERGy ^^ 

_1^00_ million Btu SQLAR ENERGY L0SS FR0M STORAGE 
_L03_ million Btu SQLAR ENERGY L0SS IN TRANSPORT 
K47_ million Btu C0L| _ ECT0R TQ ST0RAGE L0SS 
nl lion Btu C0LLECT0R TQ LQAD LQSS 
_N^A. million Btu C0L| _ ECT0R TQ Dm lQS$ 

10 

nl lion Btu C0L| _ ECT0R TQ SRACE HEATING loss 



0, 

_j^ rrr 

% 



N, 



10 

^^ million Btu COLLECTOR TQ $pACE C00LING LOSS 

lo 

_0^56 million Btu s TQ LQAD LQ$S 
14 * 

_*_ million Btu ST0RAGE T0 mw lQ$s 

lo 

— million Btu STORAGE TO SPACE HEATING LOSS 

14 lo 

N . A . million Btu $T0RAGE TQ SpACE C00LING L0S s 

-0.01 million Btu 

minion D ™SOLAR ENERGY STORAGE CHANGE 

lo 

* - Denotes unavailable data e_6 
N.A. - Denotes not applicable data 



UNIVERSITY OF FLORIOA 



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